586 ON THE YOUNG OF THE ROBBER CRAB. 



taken at night by torchlight running about the rocks at the brink of the sea, the 

 females having brown eggs attached to the abdominal limbs in large masses. 



The copulation is at present unknown. There are no special organs to this end in 

 the male, which is withcjut abdominal limbs save on the sixth segment, and has no 

 such structure on the co.xopodite of the last leg as is found, for instance, in Coenobita 

 perlatus. This joint is, however, somewhat modified, being produced into a conical 

 process and connected with its fellow across the middle line. The process of coition 

 probably takes place inland, as females with eggs are fnund at long distances from 

 the coast (22). • 



The eggs are borne in grape-like bunches attached to the long hairs on the great 

 biramous limbs of the second, third, and fourth abdominal segments. Each hair forms 

 the stalk of a bunch, and by displacing the eggs it can be seen that they are not 

 arranged evenly, but are in clumps of about half-a-dozen at intervals along the hair. 

 The mode of attachment is that commonly found among Decapods, namely by pro- 

 longation of the outer shell into a hollow stalk. The shape is ellipsoidal, and the 

 dimensions 8 mm. by •? mm. (in spirit). When the young begin to hatch the mother 

 washes them off into the water. 



The embryonic skin must be very early lost, for, out of a large number of ne\vl\-- 

 hatched young, every one had already thrown it off. Luckily the material on which 

 the present account is based, contained, among a number of unripe eggs, one which was 

 nearly read\- to hatch. By opening this egg a specimen still in the first skin was 

 gotten. In this it could be seen that the shape of the skin resembled on the whole 

 that shown for other pagurine zoaeas b\- G. 0. Sars (27). Further allusion will be made 

 to it in describing the telson of the free larva. 



The first zoaea (Fig. 1), which is in no way remarkable in general appearance, has a 

 total length of rather over 3^ mm., more accurate measurement being impossible in the 



Fig. 1. 

 Zoaea of the Robber Crab. The carapace has lifted somewhat from the body. 



preserved specimens owing to the lifting of the carapace from the body. The carapace 

 is like that of other pagurine zoaeas in its principal features. There is a moderately 

 long rostrum, broad at the base but narrowing rapidly towards the free end. With this 

 exception the carapace is without spines. The hinder edge is hollowed and at each side 

 of the indentation is a rounded side-lobe. The length in the middle line, measured from 

 the tip of the rostrum to the hinder edge, varies slightly but is always rather under 

 li mm. 



